This invention relates to electronic assemblies and, more particularly, to a method of assembling components to circuit boards.
A common approach to the organization of electronic systems is to divide the system into a number of subsystems, and to place each subsystem onto a circuit card. For example, in a computer the central processor and its associated circuitry may be placed onto one card, the display graphics drivers may be placed onto another card, the driver for each input/output device may be on an individual card, and power-related functions may be on another card. On each of the cards, components are affixed to the surface of the card, and linked by wires or electrically conductive paths termed traces. The cards are linked by wires or by plug-in connectors. This architecture provides an organization which permits individual functions to be repaired, added, or removed easily.
To fabricate a system having this type of architecture, the components are individually fabricated, and the cards are separately fabricated with the appropriate connectors and traces. The components are attached to the card, either semipermanently with mechanical attachments or permanently with adhesives. Lastly, any permanent electrical connections are made by soldering. When the electronic system is to be used in applications which must remain reliable for extended periods and/or are subjected to mechanical loadings such as shocks, it is preferred to make all attachments permanent in nature, with the components adhesively bonded to their circuit boards and the electrical interconnects permanently soldered.
Thousands of circuit boards most be fabricated for use in complex systems such as communications satellites. In the conventional practice, the components are adhesively attached to the circuit cards, and this subassembly is cured. Electrical connections are thereafter made by soldering using pre-tinned bonding pads on the circuit card. This process is time-consuming and adds significantly to the cost of the electronic systems.
There is a need for an improved approach to the assembly stage of the fabrication of electronic circuit cards. The present invention fulfills this need, and further provides related advantages.